1. Field of the Invention
The present invention relates to automate material handling systems for semiconductor panels and, more particularly, to a growth model automated material handling system.
2. Earlier Related Developments
Historically, there have been two overriding desires amongst consumers that have fueled the advancement of microelectronic devices. These desires have been for minituarization of the devices, and for ever lower prices. Manufacturers have attempted to satisfy these desires, and at least with respect to prices, have reacted by slashing the prices. However, this in turn has had a significant detrimental impact to manufacturer bottom lines. It is clear, that manufacturers that will succeed in the future will be those that can reduce costs across all levels of the manufacturing process involved in producing the microelectronic devices. A significant part of this cost is associated with and locked into the cost of the semiconductor fabrication facility itself and the processing tools and associated support systems installed therein for use in semiconductor fabrication. Referring to FIG. 1, there is shown a perspective view of a representative conventional semiconductor fabrication facility 1. The fabrication or fab facility 1 has a number of fab bays 2 arranged in the facility in a desired array. The fab bays 2 include vacuum and atmospheric processing tools 3, 4 where the semiconductor devices are manufactured. The fab facility 1 also has an automated material handling system installed therein for transporting the semiconductor material to and from the processing tools 3, 4 to effect manufacture of the semiconductor devices. The conventional material handling system in the fab facility shown in FIG. 1, generally includes stockers 5, interbay transport system 6, and intrabay transport system 7. In this arrangement, the stockers 5, used to store the semiconductor devices between various processing evolutions, are located adjacent the opening of the fab bays 2 on a common passage linking the fab bays 2. The interbay transport system 6 is installed in the common passage and connects the stockers 5. This allows semiconductor devices to be transported, by suitable vehicles traveling on the interbay transport system 5 between stockers 5. The intrabay transport system 7, as seen in FIG. 1, has sections 7A–7B disposed in the fab bays linking the stockers 5 adjacent the opening of a given bay to the processing tools 3, 4 in that bay. Thus, semiconductor devices can be transported between the stockers 5 of a bay and the processing tools in that bay with suitable vehicles traveling on the corresponding section 7A–7F of the intrabay transport system.
As can be realized from FIG. 1, the automated material handling system is one of the significant factors in the efficient fabrication process in the fab facility, operating much like the circulation system in a body. With conventional automated material handling systems, the fabrication facility is built and planned around the handling system. The reason at least in part, is that conventional automated material handling systems have a configuration that makes the system itself very inflexible to changes in fabrication requirements or layout changes. Installation of conventional automated material handling systems proceeds in generally one way which results in significant “down” or “idle” time for large portions of the fab facility. FIGS. 2A–2C are schematic plan views illustrating a conventional fab facility I1 (generally similar to fab facility 1 in FIG. 1) at three successive stages during installation of the conventional automated material handling system. As seen in FIG. 2A, in the conventional manner, the work in process storage or stockers I5 and the interbay transport I6 are installed first. Stocker and interbay transport parameters may have to be planned twelve months or more in advance of facility ramp up. The stockers and interbay transport materials are purchased and installed long before tool fit-out. The stockers I5 and the complete interbay transport I6 are installed in anticipation of fabrication layout (in this example there are eight fab bays I8A–I8H shown in phantom), but it is the stockers and interbay transport arrangement itself that defines the fab layout. As can be realized from FIG. 2A, at this stage even though the full complement of stockers I5, and the interbay transport I6 is complete, there is still no automated tool loading or unloading. Any semiconductor production in the fab facility at this stage involves mostly manual tool loading and unloading. FIGS. 2B–2C respectively illustrate the fab facility at successive stages of the automated material handling system installation. In FIG. 2B, some of the intrabay transport sections I7C, I7E–I7F have been installed in the corresponding fab bays I8C, I8C–I8F. At this stage the material handling system is capable of providing only partial automated tool loading. Hence, some manual tool loading/unloading may have to be employed in some areas of the fab facility where processing is desired. Indeed, even in bays where the intrabay transport sections have been installed, fab speed remains significantly limited or constrained from the anticipated fab speed when material handling in the facility is fully automated because of the interface during semiconductor fabrication between bays with manual tool loading/unloading and the automated bays. Intrabay transport sections I7A–I7H have been installed in all desired fab bays I8A–IH of the facility. It is only at this stage that automated tool loading/unloading is available at any desired location of the fab facility. Fabrication “ramp-up” can now occur in the facility. However, the cost due to having large portions of the fab facility substantially idle or at best using manual tool loading/unloading cannot be recovered, and can only be ameliorated by raising the prices of the semiconductor devices produced after fab “ramp-up”. The present invention overcomes the problems of the conventional systems as will be described in greater detail below.